Peaking ballast



Oct. 11, 1960 A. R. DAVIS 2,956,249

PEAKING BALLAST Filed March 9, 1956 IN V EN TOR.

United States Patent Ofitice Patented Oct. 11, 1960 PEAKING BALLAST Ariel R. Davis, 3687 S. State, Salt Lake City, Utah Filed Mar. 9, 1956, Ser. No. 570,515

4 Claims. (Cl. 336-165) This invention relates to ballasts for dimming fluorescent lamps.

An object of the invention is to provide ballast means that will ignite a fluorescent lamp over a range of intensit-ies of illuminations.

Another object of the invention is to provide an inductive means to vary the intensity of illumination of a fluorescent lamp over a wide range.

Another object of the invention is to provide a ballast for fluorescent type lamps that produces a sharp voltage pulse for igniting the lamp over a wide range of intensities of illumination.

A further object of the invention is to provide an inductive current limiting means that will ignite a fluorescent lamp at very low intensities of illumination with low R.M.S. voltages.

Other and further objects of the invention will be apparent from the following description taken in connection with the drawings in which:

Fig. 1 illustrates one embodiment of the invention with the associated circuit;

Fig. 2 is a sectional View of the ballast taken along lines 22 of Fig. 1;

Fig. 3 is another embodiment of the invention;

Fig. 4 is a sectional view taken along lines 4-4 of Fig. 3;

Fig. 5 illustrates another embodiment of the invention; and

Fig. 6 illustrates a top fragmentary view of a portion of the reactor core.

Referring to Fig. 1, there is shown a ballast 10 comprising a laminated ferromagnetic core comprising stacked laminations forming E-shaped core portions 11 and 12 and a center portion 13. The portion 11 has end legs 14 and 15 and an intermediate leg 16. The portion 12 has end legs 17 and 18 and an intermediate leg 19. The end leg 14 and intermediate leg 16 are connected by side leg 20, and end leg 15 and intermediate leg 16 are connected by side leg 21. The end leg 17 and intermediate leg 19 are connected by side leg 22, and end leg 18 and intermediate leg 19 by side leg 23. The center portion 13 has laminated sections 24 and 25. Section 24 extends between end legs 14, 17 and intermediate legs 16, 19 and section 25 between end legs 15, 18 and intermediate legs 16 and 19.

Clamping means 26, 27 are provided at the ends of the ballast to securely hold the E-shaped portions and center portion together and securely hold the end legs 14, 15, 16, 17 in magnetic contact with the center portion. The intermediate legs 16, 19 are spaced to form air gaps 28 and 29 between the intermediate leg and the center portion.

The sections 24 and 25 are spaced to form air gaps 30a, 30b bridged by a lamination 31 or thin piece of core material. The gaps 30a, 301) are positioned intermediate to the legs 16 and 19 to provide flux paths between section 24 and intermediate legs 16 and 19 and section 25 and the intermediate legs.

The end and intermediate legs space the side legs from the center portion to form spaces for windings. The reactor or ballast winding 32 is positioned around the section 24 and transformer or main winding 33, and filament windings 34, 35 are positioned around section 25. The section 24, end legs 14, 17, side legs 20, 22 and intermediate legs 16, 19 form parallel magnetic paths for the flux created by current through the reactor winding. Section 25, end legs 15, 18, side legs 21, 23 and intermediate legs 16, 19 form parallel flux paths for the main winding and filament windings. The reactor flux path and main flux path have the air gaps 28, 29 therein to increase the reluctance of the paths. Flux paths for both the reactor winding and main winding are provided by the center portion and the end legs 14, 17, side legs 20, 21, 22, 23 and end legs 15, 18. The flux from the main winding passes through the lamination 31, section 24, legs 14, 17, side legs 20, 22, 21, 23, and end legs 15, 18 to the section 25. The air gaps 28, 29 present a high reluctance to the initial flux of the main winding and the lamination 31 presents a low reluctance path. Since the amount of steel in the lamination 31 is small, the lamination saturates on a low amount of flux. The lamination then presents a high reluctance to the flux of the main winding and the flux then passes through the gaps 28, 29 and the side legs 21, 23. Flux from the main winding also passes through the gaps 30a, 30b, center portion 24 and legs 14, 17, side legs 20, 22 to the side legs 21, 23. The amount of flux depends on the reluctance of the path through the gaps 30a, 30b and through the gaps 28, 29. The flux of the reactor winding passes through the gaps 28, 29 and side legs 20, 22. While the flux is increasing or decreasing through the lamination at each end of the flux cycle of the main winding, a high voltage is produced in the reactor winding. On saturation of the lamination 31, the flux change ceases and the high voltage stops quickly to provide a sharp narrow peaking voltage. The gaps 30a, 30b preferably provide a high reluctance to the flux passing through the section 24 created by winding 32. The flux path through the gaps 28, 29 is lower than the flux path through the gaps 30a, 30b. The gaps 28, 29 and the gaps 30a, 30b may have a reluctance relationship so that a portion of the flux from the main winding passes through gaps 30a, 30b to induce voltage in the reactor winding. This voltage is additive to the variable input voltage to provide the necessary illuminating voltage. The relation of the number of windings in the main winding 33 and reactor winding 32, and the rate of change of flux threaded through the lamination 31 creates a voltage sufficient to ignite the tube.

The ballast 10 may be connected to the lamp 40 in several different ways. Themain winding 33 may be connected by lines 41 and 42 across the input terminals 43, 44. An alternating voltage may be supplied to the terminals 43, 44. This voltage may be of the order of volts and have a frequency of 60 cycles per second corresponding to the usual domestic and commercial voltages. An autotransformer 45 is connected across the terminals 43, 44 and has a variable contact 46. The winding of the autotransformer is extended to provide a booster section 45a and increase the voltage range of the autotransformer to volts. The induced voltage in the reactor winding may be 85 volts to provide the 230 volts for full illumination. However, the gaps 30a, 30b may have a reluctance that reduces this value. A booster winding may then be added to the main winding to provide the necessary illuminating voltage. The filament windings 34, 35 are connected to the cathodes 46, 47, respectively, of the lamp 10 by leads 48a, 48b and 49a, 49b. The main winding 33 is connected to lead 49b and the reactor winding 32 is connected to lead 48a by line 50. The other end of reactor winding 32 is connected to contact 46 so that the voltage applied to the reactor winding 32 and lamp 40 in series may be varied between 85 volts and 230 volts. Thus the intensity of illumination of the lamp may be varied over a range of 500 to 1.

In Figs. 3 and 4 another embodiment of the ballast is shown in which there is a center member 60 made of stacked steel laminations. On each side of the center member are members of stacked steel laminations 61, 62, 63, 64, each having side and end legs. The members 61, 62 with the center member 60 form a reactor core and members 63, 64 with center member 60 form a transformer. The cores are coupled by rectangular interleaved laminations 65a, 65b. The members 61, 62, 63, 64 and laminations 65a, 65b on sides of the aforementioned members are secured together by suitable means (not shown) so that end legs 66, 67 of members 61, 62 are in contact with the center member 60 and the end legs 68, 69 are spaced to form gaps 70, 71. The members 63, 64 have end legs 72, 73 in tight magnetic contact with the center member 60 and end legs 74-, 75 spaced to form gaps 76, 77. The members 61, 63 and members 62, 64 are each respectively spaced to form gaps 78, 79. The gaps 79, 78 have a higher reluctance than gaps 76, 77 so that the flux passing through side legs 80, 81 and 82, 83 will go through the end legs connected thereto. The laminations 65a, 65b form low reluctance paths with the center number 60 to carry the initial flux of the main winding 84 and couple it with the reactor winding 85. The laminations 65a, 65b saturate on a low amount of flux and the remaining flux of the main winding passes through the path provided by the side legs 82, S3 and end legs 72, 73, 74, 75. This latter flux path has a higher reluctance than the laminations 65a, 65b flux path due to the gaps 76, 77; however, it has a higher flux carrying capacity.

The reactor winding fiux is carried by the side legs 80, 81 and end legs 68, 69, 70, 71.

In Fig. another embodiment of the invention is shown in which the magnetic flux paths of the reactor winding have a discontinuity to produce a change in flux characteristic. The ballast has a laminated center portion 90 and E-shaped portions 91, 92 on opposite sides thereof to provide parallel magnetic paths for the fluxes of the main Winding 93 and reactor winding 94. The E-shaped portion 91 has legs 95 and 96 and an intermediate leg 97. The end leg 95 and intermediate leg 97 are coupled by a side leg 98, and the end leg 96 and intermediate leg 97 are coupled by a side leg 99. The E-shaped member 92 has end legs 100 and 101 and an intermediate leg 102. The end leg 100 and the intermediate leg 102 are connected by a side leg 103, and a side leg 104. The end legs 91, 92, side legs 98, 103 and intermediate legs 97, 102 form parallel flux paths for the reactor winding 94'. A flux path for the main winding and the reactor winding is provided through the center member 90 and legs 95, 100, side legs 98, 103, 99, 104 and end legs 96, 101.

The E-shaped portions and the center portion are clamped together by suitable clamping means (not shown) to hold the end legs 95, 100, 96, 101 in tight magnetic contact with the center portion 90. The center legs 97, 102 are sli htly spaced from the center portion 90 to form air gaps 105, 106. In the flux paths for the reactor Winding 94, a discontinuity is provided such as the slits or air gaps 107, 108 in the side legs 99, 104, respectively. On each end of the gap 107 are laminations 109, 110, and at each end of gap 108 are laminations 111, 112. The initial flux passing through the side legs 99, 104 thread through the laminations 109, 110, 111 and 112. These laminations provide a low reluctance for the initial flux provided by the main Winding 93. On saturation of these laminations, the flux path is determined by the reluctance of the air gaps 107, 108. Since these gaps are wider and have a higher reluctance than the gaps 105, 106, the main portion of the subsequent increase in flux of the main winding 93 passes through the legs 97, 102. Some of the flux passes through the gaps 107, 108 and the center portion to induce voltage in the reactor Winding additive to the input voltage for providing the required illuminating voltage. Thus, initial ly there is a flux change through the reactor winding 94 creating a voltage therein. But on saturation of the laminations 109, 110, 111, 112, this flux change ceases and the flux passes through the gaps 105, 106. On passage of arc current through the winding 94, the flux created by are current must pass through the air gaps 107, 108. For this reason the saturation characteristics of the flux path through the side legs 99, 104 will be different from the flux of the reactor cores of the embodiment shown in Figs. 1 through 4. The air gaps 107, 103 are turned to reduce the rate of saturation of the reactor core. This characteristic is another desirable feature imparted to the ballast.

It is thus seen from the foregoing description that by inserting a discontinuity in the magnetic path cooling the main winding and reactor winding so that the rate of change of flux is abruptly altered during the flux cycle of the transformer winding and preferably during the initial stages, a peaking voltage may be induced in the reactor winding. This voltage should have maximum value in the order of 400 volts so that the lamp will be ignited at the low intensity of illumination.

The above-described ballast is compact in size and inexpensive to manufacture.

Various modifications and changes may be made without departing from the scope of the invention as set forth in the appended claims.

I claim:

1. A ballast comprising a reactor winding, a main winding, a laminated ferromagnetic core having a center member with said reactor winding and said main winding wound thereon, E-shaped core members on opposite sides of said center member with intermediate legs between said windings and end legs at each end of said windings and side legs interconnecting said end and intermediate legs to complete the magnetic path of the flux of said windings, said intermediate legs spaced from said center member to form gaps therebetween, said center member having a substantially reduced cross section to provide a flux path having an initial low reluctance and a subsequent high reluctance coupling said main winding and said reactor winding to create a sharp high voltage pulse in said reactor winding, said reduced cross section being positioned in relation to said intermediate legs so that the center member forms with the intermediate legs a flux high capacity path of a greater reluctance than the initial reluctance of the reduced cross section a d a lower reluctance than the subsequent higher rehictancc of the reduced cross section to pass the flux of the main winding so that it does not link with the reactor Winding.

2. A ballast as set forth in claim 1 wherein a low permeability cross section is provided in said center member to form said substantially reduced cross section, said reduced and low permeability cross sections being positioned between the intermediate legs so that flux paths for the main winding and reactor winding are provided in the center member and the intermediate legs for bypassing said reduced cross section.

3. A ballast as set forth in claim 2 wherein the flux path of the center member through the reduced cross section and the low permeability section has a reluctance on saturation substantially higher than the flux paths bypassing the reduced cross section.

4. A ballast comprising a reactor winding, a main winding, a laminated ferromagnetic core having a center member with said reactor winding and said main winding wound thereon, E-shaped core members on opposite sides of said center member with intermediate legs beduced cross section portion and a second non-magnetic gap adjacent to said reduced portion, said reduced portion providing a flux path having an initial low reluctance and a subsequent high reluctance coupling said main Winding and said reactor winding to create an initial flux coupling said main winding and said reactor winding and saturating said reduced section portion, said reduced portion and said second gap positioned between the ends of said intermediate legs and said intermediate legs extending on both sides of said reduced portion to overlap said center member on each side thereof to provide =flux paths of high capacity on each side of said reduced portion between said center member and said intermediate legs, said second gaps having a substantially higher reluctance than said first gaps so that on saturation of said reduced portion the fluxes of said reactor winding and said main winding pass through said first gap to produce a high voltage pulse in said reactor winding.

References Cited in the file of this patent UNITED STATES PATENTS 2,432,343 Short Dec. 9, 1947 2,578,395 Brooks Dec. 11, 1951 FOREIGN PATENTS 114,200 Australia Nov. 20, 1941 

